1. Field of the Invention
The invention relates to a method for controlling the start-up phase of a motor vehicle which is driven by an internal combustion engine, the start of the internal combustion engine occurring by means of at least one electrical machine that can be operated as a motor, and there is a preferably automatically actuatable clutch in the drive train between the internal combustion engine and the electrical machine.
The invention further relates to a method for controlling the start-up phase of motor vehicles which are driven by an internal combustion engine and comprise an automatically actuated clutch, with the internal combustion engine being accelerated by a starter from standstill at first, with the engagement process of the clutch being startable from a predetermined threshold speed in order to initiate the start-up phase and with the injection process being started at a time after a synchronization time.
The term synchronization means that the motor control unit can recognize the absolute angle in which the crankshaft of the internal combustion engine is situated momentarily. This contains the information in which part of the cycle the individual cylinders are situated. As a result of the usually employed sensor system, this is only possible after passing a certain angle after a first-time movement of the crankshaft.
The invention also relates to a method for starting an internal combustion engine for a vehicle, with the crankshaft of the internal combustion engine being connected via at least one separable clutch to a drive train comprising a transmission, which drive train comprises at least one electrical machine, with the crankshaft of the internal combustion engine being brought to a predefined starting rotating position in a start preparation phase preferably by the electrical machine, with the angular speed and the angular position of the crankshaft being determined by a vehicle speed sensor during operation.
The invention further relates to a method for reducing transmission noises for a drive train of a vehicle with an internal combustion engine acting upon a drive shaft and an electrical machine which is connected via a transfer box with the drive shaft, with an actuatable clutch being arranged between internal combustion engine and transfer box.
2. The Prior Art
In order to meet mobility requirements of the future, motor vehicles must meet a number of additional requirements. Special attention is given to disturbance caused pollution and noise in discussions on environmental policy. As a result of international treaties, the legislator has prescribed drastic reductions of the fleet emissions of CO2 and fleet consumption.
In addition to the goals under environmental policy, it is also necessary to consider the demands of the worldwide markets and the vehicle users. The trend towards more safety and comfort in the construction of motor vehicles and the increasing share of vans and so-called SUVs (Sport Utility Vehicles) lead to an increase in vehicle weights and thus make reaching consumption and emission goals more difficult. It is also not possible to entirely forget the emotional factor of mobility. Driving fun and pleasure are important aspects without which it is not possible to market cars.
In order to meet the contradictory goals of reduction of consumption and emissions on the one hand and comfort and drivability on the other hand, it is necessary to apply a systemic approach by including the entire drive train.
The functions of motor vehicles are increasingly automated. This relates especially to the process of start-up of motor vehicles. When a motor vehicle is to move from standstill with idle engine it is necessary to start the internal combustion engine first and then to engage the clutch in order to produce positive engagement between internal combustion engine and drive wheels. The time period is critical which passes between the initiation of the starting process and the start of acceleration of the motor vehicle. The acceptance of automated systems by the car driver depends essentially on whether it is managed to minimize objective criteria in respect of delay time, noise and juddering and to optimize subjective criteria.
In conventional systems, the internal combustion engine is accelerated first by the starter without performing any injection so as to avoid deteriorating the exhaust gas limit values by the emission of unburned hydrocarbons. The first injection process is performed after a synchronization time at which the phase position of the piston and the valves are in a permissible area on the one hand and the engine speed is sufficiently high to ensure secure combustion on the other hand. From the first active injection it can be assumed that the internal combustion engine will supply a positive moment. The start of the engagement process of the clutch is then started, so that after a first idle time the torque can be transmitted onto the drive wheels of the motor vehicle and the acceleration process starts. The total duration until the start of the acceleration of the motor vehicle depends essentially on the time which passes from the start of the process until the synchronization time. This time period depends on its part on the output of the starter, the moment of inertia and the frictional moment of the internal combustion engine, the required speed at the synchronization time and the phase position of the internal combustion engine at the start of the process.
A reaction moment occurs especially during impulse start via the drive wheels of a rolling vehicle, which reaction moment is noticed by the vehicle passengers as a disturbing jolt.
EP 0 743 216 A2 describes a hybrid vehicle with an internal combustion engine and an electric clutch motor and an electric auxiliary motor. The starting process occurs via the electric clutch motor. Clutch motor and auxiliary motor are triggered in such a way that the torque of the drive shaft acting upon the drive wheels remains constant.
U.S. Pat. No. 6,244,368 B1 describes a hybrid vehicle with an electromotor and an internal combustion engine. When the internal combustion engine is started during an electric drive mode by the electromotor, its driving power is increased to the extend of the required starting power for the internal combustion engine.
A starting and drive unit for an internal combustion engine of a motor vehicle is known from DE 198 58 992 A1, with the internal combustion engine being connectable via a crankshaft and a clutch with a drive train comprising a transfer box. The transfer box is connected with an electrical machine with which various start methods can be performed. Each start method is preceded by a start clarification phase in which the crankshaft is turned by means of the electrical machine and in which the starting conditions are detected with closed clutch, a decision on the subsequent operating phases is made and whose starting parameters are determined. The speed conditions and the speed progress on the input and output side of the clutch are detected in an electric start control device via two speed sensors on both sides of the clutch and a decision is made on the starting method to be employed in a start clarification phase and the starting parameters are determined for this.
Speed sensors used as a standard for determining the crankshaft speed for example are relatively inexpensive, but come with the disadvantage that a determination of the position of the crankshaft is only possible in an imprecise manner and above a minimum speed. Especially in the case of slowly turning crankshafts, the speed sensors can no longer be used for determining the positioning of the crankshaft. Position sensors which are able to provide precise angular information on the position of the crankshaft even at low speed or at a standstill are relatively complex.
DE 198 08 472 A1 describes a method for starting a fuel-injection internal combustion engine of a motor vehicle. In the time preceding the ignition, the engine is brought by a drive at slow speed to such a position that the piston of a cylinder stands at the upper dead center. With the ignition command, the motor is forced to perform a further small rotational movement, then there is injection and ignition. The position of the crankshaft is detected via a separate crankshaft position sensor.
WO 01/88370 A1 describes a start process and a starter apparatus for internal combustion engines, with the crankshaft being turned by an electrical machine to a predetermined starting position. The position of the crankshaft is detected by a separate rotary and position sensor which cooperates with the crankshaft. Such position sensors are relatively costly.
DE 100 62 985 A1 describes a method and a control device for determining the crankshaft angle of an internal combustion engine, with the internal combustion engine being coupled with an electrical machine, such that its rotor is connected in a torsionally rigid manner with the crankshaft. The electrical machine comprises a control device for controlling the same and an apparatus for determining the angular position of the rotor with respect to the stator. For the purpose of determining the crankshaft angle, the current angular position of the rotor is detected by the apparatus for determining the angular position and forwarded to the control device. Then the respective current crankshaft angle is determined in the control device on the basis of the detected angular position values. The crankshaft angle thus determined is then forwarded by the control device to the control unit of the internal combustion engine.
EP 1 113 169 A1 describes a starter arrangement for an internal combustion engine and a method for controlling the starter arrangement during a start and stop process of the internal combustion engine. The starter arrangement contains an electric drive system with an electrical machine which can be connected via a clutch with the internal combustion engine.
When a so-called side-mounted starter generator (SSG) is driven by the internal combustion engine via a clutch, an alternating moment is transmitted via the connecting gear between the electrical machine and the drive train, which is caused by the combustion strokes of the internal combustion engine. When a low generator moment is retrieved via the electrical machine, the transfer moment between internal combustion engine and electrical machine can change in its sign. The flanks of the interposed gearwheels which usually rest rigidly on each other under pretension can detach from each other within the scope of possible play and hit each other again, which is audible in the form of rattling. This case occurs at low speeds, especially at idling speed of the internal combustion engine.
It is the object of the present invention to minimize the time until the start of the power transmission and thus the acceleration of the motor vehicle by optimizing the control of the start-up phase. It is a further object of the invention to at least reduce the reaction moment during impulse start. It is also an object of the invention to minimize the time until the start of the power transmission and thus the acceleration of the vehicle by optimizing the control of the start-up phase and especially the engagement of the clutch. It is a further object to enable in the simplest possible way a positioning of the crankshaft for a starting process. It is further an object of the invention to avoid rattling of the gearbox especially in idling of the internal combustion engine.